No FWD Gears ? Fresh LS/4L80E Swap
I recently finished a C10 Build w/ the below details. The observable symptom is that the Wheels will turn in any FWD gear when truck is on jack stands. When on the ground, the truck will NOT move in any FWD Gears, so it appears the trans is slipping. Reverse functions normally w/out issue. When unplugging the Round Connector to the Transmission (if I understand correctly this defaults trans to 2nd gear), the observable symptoms are the same? still will not move in FWD. W/ round connector connected, I can manually engage all 4 gears via the HPTuners Scanner, and hear the Solenoids Operating (no solenoid engagement in 2nd). Additionally I can hear the TC Solenoid engaging when activating through the software. I have confirmed that the transmission level is correct (using stock dipstick).
Engine ? 2001 6.0L LQ4 (2001 Silverado)
ECU ? 2002 4.8L 4L60E (OS 12212156) ? Custom 3 Bar OS has been installed due to this being a Turbo?d application.
Trans ? 2000-2001 4L80E w/ TransGo HD2 Shift Kit installed by myself (Trans came from friend of a friend, and was sold as is, but was not know to have any issues and was a pullout from a local salvage yard)
Shifter ? Lokar Tunnel Mounted w/ Mechanical Linkage (rod and heim). PRNDL position working correctly when shifting, as viewed through HPTuners Scanner as detenting through positions of shifter.
Tuning Process ? I did NOT do a Segment Swap. Rather I did a Comparison Log through the HPTuners Software, comparing against the 2001 6.0L 4l80E Software (OS12208322), for which would be appropriate for the 4L80E Transmission. I applied the differences for the Transmission folder/section of the software. In reading multiple posts/literature, I was hesitant to pursue the Segment Swap, and demised that applying the Compare differences was essentially doing the same thing.
Codes Present ?
- P0740 - Torque Converter Clutch Circuit Malfunction
- P0785 - Shift/Timing Solenoid DTC Trouble Code
My Questions Are:
- Is a Segment Swap still required, considering I updated the software using the Compare features to update all parameters from the 4L60E to the 4L80E?
- W/ the two codes that are present, is it apparent to anyone what my issue is?
- By unplugging the round connector and w/ the observable of wheel spin on the jack stands in fwd and none on the ground, have I confirmed that this is a mechanical problem and the trans will need to come out?
- Is a pressure test suggested as the next step in diagnosing the issue? IF so, does anyone have a guide/recommendation on going about this. If I understand correctly there is a port in the Drivers Side that I will plumb a gauge to check pressure in each gear? Low Pressure would indicate a leak from a sealing ring or clutch pack, etc?
Ive been working on this Turbo C10 build for about 7 years now, and was excited to take the truck for its first drive this past weekend. I was quickly discouraged to find that FWD gears weren?t working. Any help/advice from the group would be very much appreciated.
